Dolphins are highly intelligent marine mammals and are part of the family of toothed whales that includes orcas and pilot whales.The first cetacean was Pakicetus, which lived 55 million years ago. It was a shore animal with well-developed four limbs. The first dolphins (and toothed whales) are considered the Squalodontidae, which lived 33 to 15 MA years ago. They were 3 m (10 ft) long and had large teeth.
There are 32 dolphin species. The smallest living dolphin is a porpoise, vaquita (Phocaena sinus) from the Sea of Cortez: up to 1.5 m (5 ft) in length and 50 kg (110 pounds) in weight. The largest dolphin is orca: males can be 8 m (27 ft) long and weigh 6 tonnes.
The dolphin is the only mammal that gives birth with the tail first instead of the head.
Dolphins don’t smell very well.
Dolphins can stay up to 15 minutes under water, but they cannot breathe under the water.
Dolphins consume a variety of prey including fish, squid and crustaceans.
Most species live in shallow areas of tropical and temperate oceans throughout the world. Five species live in the world's rivers.
Young dolphins will remain with their mother for a period of 2 or 3 years.
There are two stomachs for dolphins just like for cows. The first one stores the food for them and the second one is where digestion takes place.
Dolphins can swim at a speed of up to 25 miles per hour for a long time. This is about 3 times faster than the fastest humans in the world.
Dolphins often display a playful attitude which makes them popular in human culture. They can be seen jumping out of the water, riding waves, play fighting and occasionally interacting with humans swimming in the water.
Dolphins have excellent eyesight and hearing as well as the ability to use echolocation for finding the exact location of objects.
The average lifespan of a dolphin is 17 years. However, some of them that have been observed in the wild lived about 50 years.
A dolphin needs to get air at different intervals. Some need air every 20 seconds but others only need it every 30 minutes.